I know a bloke who used to work for Waterford Crystal, he's on my Useful allies list
glass can be fairly simple to make in some of is more basic forms, bear in mind that even Medieval societies had Glass, its main ingridients are white Sand, Lime, Potash, and some Minerals (from my understanding a few Aluminium cans wil suffice here), then its just a case of grinding it all into a fine powder heatin it up and working itto the shape you want. Simples
I do agree that the technology we have today means that with a little knowledge we can live very comfortable lives, and with the Satelite infrastructure inplace we may well be able to continue these interweb conversations longafter the demise of civil society.
What most scares me is the Idiots, everyone knows a few morons who would burn all the books in the world out of pure spite, these thickos may get their way
on the other point
there may well be no NEED to fight each other, however the base nature of humanity means that we may simply WANT to fight each other.